Process of making higher fatty acid anhydrides



Patented June 24; 1941 PROCESS OF MAKING HIGHER FATTY ACID ANHYDRIDES Horace Finningley Oxley and Edward Boaden Thomas, Spondon, near Derby, England, assignors to Celanese Corporation of America, a corporation of Delaware No Drawing. Application December 7, 1938, Se-

rial No. 244,384. In Great Britain December 6 Claims.

This invention relates to the manufacture of onhydrides of higher fatty carboxylic acids.

We have iou ti that the production of carboirylic acid anhydrides from acetic anhydride or other anhydride of a lower acid, 1. e. one containing a smaller number of carbon atoms than the acid corresponding to the anhydride required, and the acid of the anhydride desired can be edected on the commercial scale simply, economically and so as to obtain a high conversion oi the higher acid which is in general much more expensive than acetic anhydride, by passing the vapours oi the lower anhydride through the higher acid maintained in the liquid phase, preferably at a temperature above the boiling point of the lower anhydride under the working conditions, and allowing the vapours of the lower acid produced to escape from the reaction zone.

The higher acid, it not liquid at ordinary temperatures, is preferably maintained in the liquid phase by fusion though the use of inert solvents is not excluded.

The following examples illustrate the invention: I

Example 1 acid. During the progress oi the reaction, the

proportion of acetic anhydride gradually rises finally approximates to the 99% concentration oi the feed showing that substantially the Whole oi the lauric acid has been converted.

the temperature of the liquid in the distillation vessel is finally raised to l50 C. in order to remove unreacted acetic anhydride,

Example 2 ihliiill parts by Weight of palmitic acid are at lilo-20d U. in a distillation apparatus ilor iii hours at atmos glheric pressure, While admitting, below the suriace oi the molten acid, lifl dd parts by Weight oi 9.5% acetic anhydridc.

the distillate at first consists mainly of acetic acid but the concentration oi acetic onhydride eventually attains The product remaining in the distillation vessel consists largely of palmitic anhydride and is freed from traces of acetic anhydride by crystallisation from ethyl acetate.

A still higher conversion can be obtained by carrying out the reaction under reduced pressure at a lower temperature.

Example 3 Example 4 1,136 parts by weight of stearic acid is heated in a vacuum distillation apparatus at 90-100 (8 under a pressure of 10-20 mm. and 1,000 parts by weight of 98.4% acetic anhydride is introduced below the surface of the molten acid during 4 hours. The temperature is then raised for a short time to 200 C. in order to expel the small quantity of unreacted acetic anhydl'ide. The yield of stearic acid is substantially theoretical and the conversion over 90%.

The process can also be carried out continuously, A convenient method of doing this isto introduce the vapours of acetic anhydrideheor the bottom of a column maintained at a temperature above the boiling point of the anhydride and to cause the liquid higher acid to drip from plate to plate down the column irom a point near the top. The vapours of acetic anhydride and acetic acid pass from the top .oi" the column to condensation apparatus or, ii desired," to o iractionating column and the higher onhy dride (which may he in admixture with some unchanged higher acid or may be substantially free from higher acid) is drawn 0d irom the bottom of the column.

The invention is applicable to the production oi carbosylic acid anhydrides other than those specified above, for example those of propionic, normal and iso-butyric, caproic, caprylic, capric and myristic acids, of acids containing aromatic groups, for example benzoic and phenyl acetic and 05- and B-naphthoic acids, oi unsaturated acids, for example oleic and cinnamic acids, and

01' acids containing more than one carbonyl group, for example succinic acid. The invention is of particular importance in the production of anhydrides of fatty acids containing at least 8 carbon atoms. Preferably, as indicated above, acetic anhydride is employed as the lower anhydride since this is the most readily available of such anhydrides. Other lower anhydrides can, however, be employed in place of acetic. v

Having described our invention, what we desire to secure by Letters Patent is:

1. Process for the production of adrides of carboxylic acids which comprises causing a carboxylic acid to react with the anhydride of a lower fatty acid .to produce the dride of the higher acid together with the lower acid, by introducing the vapors of the lower dride below the surface of a, body of the higher acid maintained in the molten state above the boiling point of the lower anhydride, and allowing the vapors of the lower acid produced to escape from the reaction zone.

2. Process for the production of anhydrides of carboxylic acids which comprises causing a mboxyllc acid to react with the anhydride of a lower fatty acid to produce the ahhydride oi the higher acid together with the lower acid, by introducing the vapors of the lower anhydride below the surface of a body of the higher acid maintained under reduced pressure in the molten state above the boiling point of the lower anhydride at said reduced pressure, and allowing the vapors of the lower acid produced to escape from the reaction zone.

3. Process for the production of an dride of a fatty acid containing at least eight mrbon atoms, which comprises causing said acid'to react with acetic anhydride to produce the desired anhydride together with acetic acid by introducin: the vapors of acetic anhydride below the surc eeses Eace' of a body of the higher acid maintained under reduced pressure in the molten state at a above the boiling point of acetic an hydride at said pressure, and allowing the vapors of acetic acid produced to escape from the reaction acne.

Process for the production of stearic anhydride, which comprises causing stwric acid to react with acetic anhydride to produce stearic anhydride and acetic acid by introducing the vapors of the acetic anhydride below the surface of a body of stearic acid maintained under reduced pressure in the molten state at a temperature above the boiling point oi. acetic armydride at said pressure, and allowing the vapors of acetic acid produced to escape from the reaction zone.

5. Process for the production of palmitic anhydride, which comprises causing palmitic acid to react with acetic anhydride to produce palmitic anhydride and acetic acid by introducing the venom of the acetic anhydride below the surface of a body of palmitic acid maintained under reduced pressure in the molten state at a temperature above the boiling point of acetic anhydride at said pressure, and allowing the vapors of acetic acid produced to escape from the reaction zone.

6. Process for the production of lauricanhydride, which comprises causing lauric acid to react with acetic anhydride to produce lauric anhydride and acetic acid by introducing the vapors of the acetic anhydride below the surface of a body of lauric acid maintained under reduced pressure in the molten state at a temperature above the boiling point of acetic anhydride at said pressure, and allowing the vapors'of acetic acid produced to escape from the reaction zone.

HORACE FINNINGLEY OXLE'Y. EDWARD BOADEN THOMAS. 

